Direct-injection is becoming increasingly popular as a method of applying agricultural compositions. In this method, the composition is injected directly in a spray line without pre-dispersion in a spray tank containing water, and the spray tank serves merely as a reservoir of water. One significant advantage is that no agricultural composition enters the spray tank, and accordingly clean out of the spray tank is not necessary. Any unused composition can be easily stored and reused because it was not contacted with water or mixed with other compositions.
Because the hold-up time between injection and spraying is short, the composition must disperse almost instantaneously. Also, small amounts of composition must be metered accurately. For these reasons, liquid formulations such as emulsifiable concentrates (ECs) and suspension concentrates (SCs) have been preferred for direct injection. However, it would be advantageous to directly inject solid and particularly granular compositions because they have many desirable characteristics relative to liquids, including easier handling, storage, package disposal and less potential for worker exposure.
A tapered screw apparatus for direct-injection of granular materials is disclosed in "Direct Injection of Dry Flowable Agricultural Pesticides", Pesticide Formulations and Applications Systems, Vol. 10, ASTM STP 107B, Hart and Gaultney (1990). The present invention is an improvement of the apparatus disclosed therein and provides a simple, practical apparatus and method for direct-injection of particulate compositions.